Source apportionment and oxidative potential of PM₁ and PM_2.5 in Seoul, South Korea

Particulate matter (PM), especially PM_2.5, has been widely studied due to its adverse health effects, whereas PM₁ has been relatively understudied. This study investigated the chemical constituents, source apportionment, and oxidative potential of PM₁ and PM_2.5 to assess the need for research and management of PM₁. PM samples were collected in Seoul, South Korea, from June 2021 to March 2022 and analyzed. The dithiothreitol (DTT) assay was applied to evaluate the oxidative potential of the cold-season samples. Dispersion-normalized positive matrix factorization (DN-PMF) resolved ten sources common to both sizes: secondary nitrate, secondary sulfate, motor vehicle, biomass burning, incinerator, industry, coal combustion, soil, oil combustion, and aged sea salt. The average PM₁/PM_2.5 mass concentration ratio was 0.75. Secondary nitrate showed the highest PM₁/PM_2.5 contribution ratio (0.89), whereas industry, soil, oil combustion, and aged sea salt exhibited relatively low ratios (≤0.6). The DTT assay showed that PM₁ exhibited higher oxidative potential per unit mass than PM_2.5. Multiple linear regression identified secondary nitrate, biomass burning, industry, coal combustion, and soil as major sources explaining oxidative potential of PM₁. For PM_2.5, secondary nitrate, biomass burning, incinerator, industry, and soil were important. Biomass burning showed the highest standardized coefficient in both sizes, indicating it was the major cold season contributor to oxidative potential. Continued research on PM₁ will provide valuable insights into source characteristics of PM and its health effect. Regarding PM₁ management, the overlap in major sources with PM_2.5 suggests that source-specific management would be effective for managing PM₁ and PM_2.5 simultaneously.